Radio Technology Day – by Phil Parkman G3MGQ

Geoff Collins, the Principal and science teacher at Charters Ancaster, a small independent preparatory school in Bexhill, was looking for someone to help them with a radio day in their Year 6 Technology Week this year. Jakey, G3JKY, who had played trombone in Geoff’s jazz band, suggested HERC. It turned out that Geoff had previously been Head at Hollington Primary where the la te Colin May, G3KMP, had been his deputy – it’s a small world.

Two weeks later, William (G8CMK), Thelma (G8SBJ) and I rolled up after school to see the site and discuss what sort of thing Geoff would like us to do. The school, near Bexhill High School, is in a fine old house facing the Channel and about 33m ASL, according to Google Earth, with some fine old oak trees about 45m from the house across the back lawn; a very nice radio location. In the following month, whilst I prepared some activities and arranged some skeds, William sorted out a means of getting an 80m antenna up to a decent height – a task that proved not quite as easy as it would first appear when collateral damage has to be avoided! The solution proved to be a football in a string cage, punted well up into the tree, as it was heavy enough to penetrate the curtain of peripheral twigs and drop down over a substantial bough without getting stuck.

I built a 129ft Off-Centre Fed Dipole, fed with 300 Ohm ribbon 16ft from one end, which EZNEC predicted should match 300 Ohms on 3.7MHz at a height of 30ft. I chose this configuration so that the feed was close to the upstairs classroom, with a lightweight feeder to avoid height loss and balanced so there was no RF earth problem, as one can get with an end feed and which we wouldn’t have time to check & fix on the day. In practice, I found it difficult to get a low SWR with the twin wire connection on my MFJ948 ATU, but William’s venerable KW107 tuned it to better than 1.1

For VHF, Mike (M0EDU) brought his J-pole which we mounted on the window sill atop two swaged 5ft poles – not ideal as it was then only at roof level but it still pulled in the local repeaters OK. The intention was to track Steve (M0SSR) on his way to Portsmouth, demonstrating the loss of signal beyond line-of-sight and extending the QSO through the repeaters. Unfortunately Steve’s mobile transceiver kept blowing fuses, so we didn’t make that contact. Mike also set up his 3cm ATV in the grounds with his receiver alongside the HF/VHF rig, my IC706 Mk2g. His ATV illustrated the principles of CCTV surveillance and the children had fun working out where the 3cm dish was located.

Whilst the team completed setting up, Geoff gave an introduction on the diverse uses of radio communication and outlined the day’s activities which included a break for a rehearsal for their music concert the next day and the arrival of a genuine Model T Ford, lovingly restored by a couple of local enthusiasts.

I then explained the way radio waves travel depends on the state of the ionosphere and hence who we can contact depends on frequency and the time of day. We then tuned around 3.7MHz, hearing French and German amateurs, identifying them by their language and by their callsigns. We then had an excellent QSO with G3JKY, with the children asking him lots of questions about amateur radio and his other interests. George, G6PHH, in Boston came back to our CQ call, being interested of course in our callsign, G6HH. I was able to show the children on Google Maps that George was in Boston Lincolnshire, not Boston of the tea party fame in Massachusetts USA, providing an impromptu geography lesson.

After a break for lunch, Jakey joined us and talked to the children about Morse and illustrated it by making contact with G6XJS on 3.552MHz using a bug key. I then called Iain, M1000/P, who had agreed to call us from the Norman Lockyer Observatory in Sidmouth, signing GB2NLO. I’d downloaded the history of the Observatory for the children and Ian filled in the details. This year is the 150th anniversary of Norman Lockyer’s discovery of Helium in the sun’s spectrum, which confirms that the sun is heat comes from nuclear fusion. Ian also explained that Galileo was the first man to use a telescope for astronomy in 1609 so, 400 years later, this is the International Year of Astronomy for which the radio section at the Observatory have a special event callsign, GB400IYA.

Jakey then made some CW contacts on 20m, mainly in the Ukraine but including RK3ZE in Gubkin. I was able to show, on Google Maps, that Gubkin is in the Russian Federation 430 miles north of the Black Sea and 1600 miles from Bexhill, thereby illustrating the propagation principles I’d talked about earlier. From Jakey’s notes, I was able to show the children that telegraphers use abbreviations just as they did when texting their friends. The pupils were then given the Morse Alphabet sheets used in the Foundation Assessment, a key and oscillator, and all had great fun sending their name in Morse code.

There was no doubt that the children enjoyed the day – they were reluctant to go home! The radio amateurs also enjoyed the day immensely, appreciating the enthusiastic support of the staff and welcoming this opportunity to show youngsters the diverse and interesting things their hobby had to offer. It was a great team effort, and I’m also grateful for the support we had from all the other members of the Club who listened out for us.

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